The Sino-Soviet border conflict (中苏边界冲突) was a seven-month undeclaredmilitary conflict between the Soviet Union and China at the height of the Sino-Soviet split in 1969. The most serious of these border clashes—which brought the two communist-ruled countries to the brink of war—occurred in March 1969 in the vicinity of Zhenbao Island (珍宝岛) on the Ussuri River, also known as Damanskii Island (Остров Даманский) in Russia. Chinese historians most commonly refer to the conflict as the Zhenbao Island incident (珍宝岛自卫反击战).[4] The conflict was finally resolved with future border demarcations.

The deterioration of Sino-Soviet relations in the late 1950s and early 1960s resulted in tensions along the 4,380 km (2,738 mi) border between China and the Soviet Union. A particularly serious incident occurred in May, 1962, when 60,000 ethnic Uyghurs in China's Xinjiang Province crossed the frontier into the Soviet Union, fleeing the desperate economic conditions. Beijing immediately accused the Soviets of subverting the Uyghur population, a charge that was later echoed in some Chinese historiography, though never independently verified.

Amid heightening tensions, the Soviet Union and China began border talks. The Chinese position was that the 19th-century treaties, concluded by Qing dynasty China and Tsarist Russia, were "unequal", and amounted to annexation of Chinese territory. Moscow would not accept this interpretation, but by 1964 the two sides did reach a preliminary agreement on the eastern section of the border, including Zhenbao Island, which would be handed over to China.

The border dispute in the west centered on 52,000 square kilometres (20,000 sq mi) of Soviet-controlled land in the Pamirs that lay on the border of China's Xinjiang Uyghur Autonomous Region and the Soviet Republic of Tajikistan. In 1892, the Russian Empire and the Qing Dynasty had agreed that the border would consist of the ridge of the Sarikol Range, but the exact border remained contentious throughout the 20th century. In the 1960s, the Chinese began to insist that the Soviet Union should evacuate the region.

In July 1964, Mao Zedong, in a meeting with a Japanese socialist delegation, stated that Tsarist Russia had stripped China of vast territories in Siberia and the Far East as far as Kamchatka. Mao stated that China still had not presented a bill for this list. These comments were leaked to the public. Outraged, Soviet leader Nikita Khrushchev then refused to approve the border agreement.

Since around 1900, after the Treaty of Beijing, where Russia gained Outer Manchuria, the east side of the border had mainly been demarcated by three rivers, the Argun River from the triparty junction with Mongolia to the north tip of China, running southwest to northeast, then the Amur River to Khabarovsk from northwest to southeast, where it was joined by Ussuri River running south to north. Because of Chinese weakness, the Ussuri River was demarcated in non-standard manner: the demarcation line was on the right (Chinese) side of the river, putting the river with all islands in Russian possession. (“The modern method (used for the past 200 years) of demarcating a river boundary “between states today is to set the boundary at either the median line (ligne médiane) of the river or around the area most suitable for navigation under what is known as the ‘thalweg principle.’[5]

China claimed these islands, as they were located on the Chinese side of the river (if demarcated according to international rule using shipping lanes). The USSR wanted (and by then, already effectively controlled) almost every single island along the rivers.

On March 2, 1969, a group of People's Liberation Army (PLA) troops ambushed Soviet border guards on Zhenbao Island. The Soviets suffered 59 dead, including a senior colonel, and 94 wounded.[citation needed] They retaliated on March 15 by bombarding Chinese troop concentrations on the Chinese bank of the Ussuri River and by storming Zhenbao Island. The Soviets sent four then-secret T-62 tanks to attack the Chinese patrols on the island from the other side of the river. One of the leading tanks was hit and the tank commander was killed. On March 16, 1969, the Soviets entered the island to collect their dead; the Chinese held their fire. On March 17, 1969, the Soviets tried to recover the disabled tank, but their effort was repelled by the Chinese artillery. On March 21, the Soviets sent a demolition team attempting to destroy the tank. The Chinese opened fire and thwarted the Soviets.[citation needed] With the help of divers of the Chinese navy, the PLA pulled the T-62 tank onshore. The tank was later given to the Chinese Military Museum.

On March 15[citation needed], 1969, the Chinese troops were repelled from Zhenbao Island with significant losses and did not return until September of that year, when Soviet border guards received the order to not open fire against them.[3]

Further border clashes occurred in August 1969, this time along the western section of the Sino-Soviet border in Xinjiang. After the Tasiti incident and the Bacha Dao incident, the Tielieketi Incident finally broke out. Chinese troops suffered 28 losses. Heightened tensions raised the prospect of an all-out nuclear exchange between China and the Soviet Union .[6] In the early 1960s, the United States had "probed" the level of Soviet interest in joint action against Chinese nuclear weapons facilities; now the Soviets probed what the United States' reaction would be if the USSR attacked the facilities.[7]

As war fever gripped China, Moscow and Beijing took steps to lower the danger of a large-scale conflict. On September 11, 1969, Soviet Prime Minister Alexei Kosygin, on his way back from the funeral of the Vietnamese leader Ho Chi Minh, stopped over in Beijing for talks with his Chinese counterpart, Zhou Enlai. Symbolic of the frosty relations between the two communist countries, the talks were held in Beijing airport. The two premiers agreed to return ambassadors previously recalled and begin border negotiations.

The Chinese believe different version of the conflict took place. The Chinese Cultural Revolution increased tensions between China and the USSR. This led to brawls between border patrols, and shooting broke out in March 1969. The USSR responded with tanks, APCs, and artillery bombardment. Over three days the PLA successfully halted Soviet penetration and eventually evicted all Soviet troops from the island. During this skirmish the Chinese deployed two reinforced infantry platoons with artillery support. Chinese sources state the Soviets deployed some 60 soldiers and six BTR-60s and in a second attack some 100 troops backed up by ten tanks and 14 APCs including artillery.[citation needed]

The view on the reasoning and consequences of the conflict differ between western and Russian historians. Western historians believe the events at Zhenbao Island and the subsequent border clashes in Xinjiang caused Mao to re-appraise China's foreign policy and to seek rapprochement with the United States,[6] while Russian historians point out that the consequences of the conflict stem directly from the desire of the PRC to take a leading role in the world and strengthen ties with the US. Such a local conflict with the USSR would be a sign of a split with the USSR and signal the US that China was ready for dialogue.[8] The PRC began ideological preparation for the split with the USSR in the late 1950s,[9] and the Soviet Border Service started to report intensifying Chinese military activity in the region during the early 1960s.

After the conflict, America showed actual interest in strengthening ties with the Chinese government by secretly sending Henry Kissinger to China for a meeting with Prime Minister Zhou Enlai in 1971, during the so-called Ping Pong Diplomacy, paving the way for Richard Nixon to visit China and meet with Mao Zedong in 1972.[10]

Serious border demarcation negotiations did not occur until shortly before the end of the Soviet Union in 1991. In particular, both sides agreed that Zhenbao Island belonged to China. (Both sides claimed the island was under their control at the time of the agreement.) On October 17, 1995, an agreement over the last 54 kilometres (34 mi) stretch of the border was reached, but the question of control over three islands in the Amur and Argun rivers was left to be settled later.

On July 21, 2008, Chinese Foreign Minister Yang Jiechi and his Russian counterpart, Sergei Lavrov, signed an additional Sino-Russian Border Line Agreement marking the acceptance of the demarcation the eastern portion of the Chinese-Russian border in Beijing, China. An additional protocol with a map affiliated on the eastern part of the borders both countries share was signed. The agreement also includes the return of Yinlong/Tarabarov Island and half of Heixiazi/Bolshoi Ussuriysky Island.[12]